Many geographic locations have dry spells and/or insufficient rainfall requiring turf and landscaping to be watered to maintain the proper health of the vegetation. Turf and landscaping are often watered utilizing an automatic irrigation system that includes a programmable controller that turns a plurality of valves ON and OFF to supply water through underground pipes connected to sprinklers. Golf courses, playing fields and other large areas typically require rotor-type sprinklers that eject a long stream of water via a single relatively large nozzle that oscillates through an adjustable arc. Smaller areas are often watered with spray heads or rotary stream sprinklers. Spray heads eject a fan-shaped pattern of water at a relatively high rate and much of this water often flows off the vegetation and/or blows away and is wasted. Rotary stream sprinklers eject relatively small individual streams of water and use less water than spray head sprinklers. In some cases drip nozzles are employed in residential and commercial irrigation systems for watering trees and shrubs, for example.
Sprinklers used to irrigate turf and landscaping are exposed to many forces and contaminants that can adversely impact the performance of the sprinklers and in some cases render them completely inoperable. Rotary stream sprinklers are especially vulnerable to impaired performance due to the ingress of dirt and grit and the build up of calcium deposits. Rotary stream sprinklers typically include a nozzle head or stream deflector having flutes formed on the underside thereof that receive water from orifices in a nozzle plate and channel streams of water radially outward onto the turf or landscaping. The flutes and orifices can become clogged with dirt and grit, particularly where the sprinkler nozzle retracts to the level of the ground. Over time, calcium and other mineral deposits can build up due to evaporation and constrict or obstruct the flutes and/or orifices, particularly when the orifices are very small as required to produce a rotary stream sprinkler with a very small flow rate. For example, a round orifice in the nozzle plate might be only 0.015 inches in diameter in order to provide a rotary stream sprinkler with a flow rate of four gallons per hour. Such a low volume rotary stream sprinkler would be particularly desirable because it could be substituted for a spray head and result in substantial water savings.
Rotary stream sprinklers either employ a reactionary drive or a gear reduction in order to slowly rotate the stream deflector to optimize the water distribution. When a reactionary drive is employed, the flutes are angled so that the water ejected by the stream deflector rotates the same. A viscous damper or friction brake must be used to slow the rotation of the stream deflector with angled flutes. In a rotary stream sprinkler with a reactionary drive, the stream deflector can pop-up from a protective outer cylindrical base when the water is turned ON, and retract into the protective outer base, thereby providing a degree of protection of the flutes and nozzle plate orifices from dirt, debris and mineral deposit build-up due to evaporation. However, pop-up operation of the stream deflector is not practical in a rotary stream sprinkler that employs a gear reduction for driving the stream deflector. Therefore it would be desirable to provide such a sprinkler with an alternate means of protecting its flutes and orifices from debris and mineral build-up due to evaporation.